1. Field of the Invention
The invention relates to an unstacker device for unstacking mailpieces, which unstacker device comprises a motor-driven feed magazine for moving the mailpieces in a stack and on edge in a certain direction towards an unstacker head suitable for separating a first mailpiece from the stack and for driving it in a direction that is transverse to said direction in which the stack of mailpieces move.
The invention relates more particularly to a mailpiece unstacker device for a machine for sorting large-format mailpieces or “flats”. A mailpiece can, in particular, be a letter in an envelope with or without a window, a magazine, a newspaper, or a catalogue in a plastics or paper cover.
2. Discussion of the Background Art
In general, in a postal sorting machine, the mailpieces exiting from the unstacker are conveyed in series and on edge so as to be brought past a read head. The read head acquires an image of each mailpiece in the series for the purpose of automatically decoding the inward sorting address or the outward sorting address of the mailpiece by Optical Character Recognition (OCR) processing. The mailpieces are then directed towards the sorting outlets corresponding to the automatically decoded addresses.
FIG. 1 shows a mailpiece unstacker device known from Patent Document FR 2 797 856 and that comprises a belt main magazine 1. The main magazine 1 comprises in particular a belt conveyor 2 that is motor driven for the purpose of moving the mailpieces in the direction indicated by arrow 6. An operator places the mailpieces 3 in a stack on edge on the belt conveyor 2 in front of a paddle 4. The paddle 4 extends in a substantially vertical plane and is disposed facing an unstacker head or plate 5. The paddle 4 is also motor-driven so as to push the back of the stack and so as to move it in the direction indicated by the arrow 6 towards the unstacker head 5.
The mailpieces forming the stack are held laterally by a jogging edge 7 that extends in a substantially vertical plane along a side edge of the belt conveyor 2. The substantially plane unstacker head 5 extends in a vertical plane that is transverse to the direction indicated by the arrow 6 and in which the stack of mailpieces 3 move on the belt conveyor 2, and is suitable for separating the first mailpiece at the front of the stack in the transverse direction indicated by the arrow 8 that is perpendicular to the arrow 6.
The unstacker head 5 is provided with two substantially rectangular openings in each of which a perforated belt 9 and one or more suction chambers or suction nozzles (not shown) are motor-driven. The perforated belt 9 and the suction nozzles co-operate to take hold of the first mailpiece of the stack by suction and to move it in the direction indicated by the arrow 8.
In operation, the stack of mailpieces 3 placed in the main magazine 1 is moved by the stepper-type motor drive means for driving the belt conveyor 2 and the paddle 4 that are actuated at the same speed. The first mailpiece at the front of the stack of mailpieces is thus brought into abutment against the unstacker head 5 so that that current mailpiece of the stack is pressed against the unstacker head 5 and is separated from the stack by the combined effect of the suction of the nozzles and of the movement of the perforated belt 9. The mailpiece is then nipped between two deformable wheels 10 disposed in alignment with the head 5, i.e. downstream from the unstacker head in the direction indicated by the arrow 8. Said wheels 10 are motor-driven so as to convey the current mailpiece downstream from the unstacker device. They are made of an elastically deformable elastomer material so that they can adapt to accommodate various mailpiece thicknesses.
The unstacking process is repeated each time a new mailpiece at the front of the stack is presented facing the unstacker head 5.
For the remainder of the sorting process, it is necessary for the mailpieces to be put in series at the outlet of the unstacker device with a constant pitch between consecutive mailpieces. Driving of the perforated belt 9 and of the suction nozzles is thus actuated and stopped at a constant rate. For example the rate is 3 mailpieces per second.
In that known device, the mailpieces of the stack are put in series continuously at a constant unstacking rate. It has been observed that a large proportion of mailpieces are not presented appropriately facing the unstacker head at the time at which they are unstacked, and, as a result, those mailpieces might be damaged or torn, e.g. when they are taken by the wheels 10, for example. It can even happen that those mailpieces cause a jam in the unstacker device, requiring action from a maintenance operator, and requiring the unstacker device to be stopped. Such action is costly and slows down the overall sorting process. That situation can be particularly frequent with mailpieces of the following types that are open: advertising brochures, magazines, etc. In addition, that type of device does not completely eliminate situations in which mailpieces are taken in bunches. The fact that the range of large-format mailpieces or “flats” to be processed can be relatively wide makes those problems even more complex to solve.
European Patent Document EP 0 562 954 describes a feed device similar to the device presented above and that further comprises a motor-driven drop-forming channel disposed between the belt conveyor and the unstacker head. The effect of that motor-driven drop-forming channel is to fan out the mailpieces as they are presented. Thus, the first mailpieces at the front of the stack find themselves less tightly stacked against the other mailpieces. In addition, presence sensors are disposed so as to monitor the inclinations of the fanned-out mailpieces, and a control unit controls operation of the motor-driven drop-forming channel and of the belt conveyor so as to fill the drop-forming channel and so as to incline the mailpieces. That above-described arrangement is suitable for certain categories of mailpiece but does not cover a broad range of mailpieces to be processed.
Unfortunately, what is suitable for one mailpiece is not necessarily optimum for another mailpiece. For example, flats slip down under their weight, magazines open and tear, etc.